The present invention relates, in general, to a system and method for cleaning and conditioning polish pads used to polish silicon wafers and semiconductors and, more particularly, to pad cleaning during polishing and pad conditioning and cleaning after a wafer has been polished with a polishing composition.
Silicon wafers are commonly used as a base on which multilevel integrated circuits are fabricated. Integrated circuits on semiconductor wafers are manufactured with a layer of an insulating layer or semi-conductive or conductive metal substrate layer. This layer can be a dielectric, such as, silica including SiO2 and TEOS. It can also be a low K dielectric, poly-silicon or metal such as tungsten, aluminum, copper and platinum.
A series of deposition and etch steps are required to form a multi-level pattern on a semiconductor wafer. Silicon wafers for the semiconductor industry must possess a high degree of surface perfection before they can be useful in the device fabrication process. A non-planar silicon wafer surface during the manufacturing process causes a focusing problem for photolithography and results in lower yield and decreases performance of the semiconductor device.
A polishing system known as CMP, referred to as either or both, chemical-mechanical planarization and chemical-mechanical polishing of non-planar wafer is utilized in a conventional process. The CMP process is used to planarize the insulating layer on a silicon wafer. A CMP process can be used for an insulating layer whether it be a dielectric material, conductive metal or semi-conductive layer. The CMP process utilizes different polishing pads and polishing compositions or slurries. Further details of CMP polishing features and operation of a polishing apparatus for a CMP process may be found in U.S. Pat. No. 5,738,574, which is incorporated by reference.
In a CMP process, the wafer is pressed against a moving polishing pad. In a CMP process, the silicon wafer, is bathed or rinsed in a polishing slurry in conjunction with an elastomeric pad which is pressed against the substrate and rotated such that the slurry particles are pressed against the substrate under load. The lateral motion of the pad causes the slurry particles to move across the substrate surface, resulting in wear, or volumetric removal of the substrate surface. Ideally, this process results in the selective erosion of projecting surface features so that when the process is completed a plane surface is produced down to the finest level of detail.
However, the CMP process generates heat due to chemical reaction and mechanical friction, which degrades the surface topography of the pad. Also, by-product of the slurry from wafer-substrate reaction produces slurry waste, which accumulates on the pad or within the pad groove and prevents even distribution of fresh slurry and degrades pad asperities. The combination of the above reactions can produce glazing of the pad. Glazing is referred to a surface phenomenon which occurs when the pad temperature during CMP is at or exceeds the pad glass transition temperature and deforms the pad material and traps slurry by-products. These slurry by-products become partially or fully fused into the surface of the pad. Glazing decreases pad asperity and increases wafer non-uniformity and defects on the wafer.
The conventional CMP process uses a conditioning apparatus, as disclosed in U.S. Pat. No. 6,217,429 or similar device using a diamond or abrasive material on a disk in contact with the polish pad to remove glaze material and by-product of CMP waste. On a buffing pad or softer pad, a brush is used instead of a diamond disk. Deionized (DI) water is normally used during pad conditioning to help lubricate the pad and to remove debris from the pad. A high-pressure DI sprayer is sometimes used to speed up the cleaning process. For metal CMP and especially for copper CMP, cleaning solution is used to speed up the cleaning and decontamination of slurry by-products from the surface of the pad.
It is known that to perform pad conditioning with a diamond disk and clean the pad groove with brushes at the same time, two separate conditioning arms or a conditioning arm with two different disks are necessary. For example, Tolles et al. (U.S. Pat. No. 5,738,574) discloses a conditioning apparatus with a conditioning arm with multiple disks and multiple polishing stations. However, having separate conditioning arms or multiple disks increases the cost of the polishing apparatus. Accordingly, it has been desired to develop a method and apparatus for polishing a semiconductor wafer that addresses the problems above and reduces glazing and the steps and costs of polishing semiconductor wafers.
The present invention provides a conditioning apparatus with interchangeable disks with different conditioning materials to condition a polishing pad. To condition the pad, conditioning disks with abrasive material, brushes, scrubbing material can be interchanged during polishing.
In one aspect the invention includes a conditioning apparatus for conditioning a polish pad. The conditioning apparatus includes a movable conditioning arm with a disk mounting apparatus, a plurality of interchangeable conditioning disks, a disk housing capable of holding the plurality of interchangeable conditioning disks, and a controller for directing and controlling the movement of the condition arm.
In a second aspect the invention includes a conditioning apparatus that includes a movable conditioning arm with a locking module for securely holding an interchangeable disk. The interchangeable disk has a mounting sprocket which mates with said locking module. The conditioning apparatus has a plurality of disk stations positioned so that the locking module of the conditioning arm can be positioned directly over any of the plurality of disk stations. A plurality of the interchangeable disks are located on the disk stations and a controller is used for directing and controlling the movement of the condition arm.
In a third aspect the invention includes an interchangeable conditioning disk for conditioning a polishing pad that has one or more conditioning materials on a surface of the disk and a mounting sprocket on a surface opposite the surface with the conditioning material. The mounting sprocket mates with a locking module of a conditioning arm.
In a fourth aspect the invention includes a method of conditioning a polishing pad which includes the steps of: a) providing a conditioning disk apparatus having a movable conditioning arm with a disk mounting apparatus and a plurality of interchangeable conditioning disks, wherein each of the interchangeable conditioning disks have one or more conditioning materials on a surface of the disks; b) placing a polishing pad on a top surface of a platen; c) mounting one of the conditioning disks on the conditioning arm; d) moving the conditioning arm and conditioning disk to a position over the polishing pad; e) conditioning the polishing pad by rotating the conditioning disk and providing a downward force on the disk and polishing pad; f) moving said conditioning arm to a position over an empty disk station; g) releasing said conditioning disk on said empty disk station; h) mounting another one of the plurality of interchangeable conditioning disks on the conditioning arm; and i) repeating steps d) through h) until said polishing pad has the desired properties.
Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, the invention being defined only by the claims following this detailed description.